An example of an internal combustion engine having a throttle valve of the general type has been described in DE-OS No. 37 11 779. The throttle valve described therein is controlled by a conventional mechanical throttle linkage and an electronic servomotor. Electronic control of the gas pedal is achieved by using the servomotor to control the throttle valve operation between the phases of the completely closed position, (0.degree. setting) and the maximum open position specified by a mechanical transducer. When the gas pedal is not being depressed, the mechanical throttle linkage (transducer) will fully close the throttle valve. In the event of a failure of the servomotor, the throttle valve is still fully operable by the manual override capability of the mechanical throttle valve linkage. Thus, the safety of a mechanical gas pedal is achieved while using the potentials of control of an electronic gas pedal.
In my copending application Ser. No. 498,341, based on European Application EP-A 89105378.7, I disclose an improvement over the throttle valve of German Patent Disclosure 37 11 779, which allows integration of an idle fuel-injection controller, a cruise control system, and an antislip control.
It is desirable to keep the throttle valve open a slight degree (preferably between 0.degree.-10.degree.) during idle conditions to ensure that the engine remains ready to rev up.
Imprecise or inadequate control of the throttle valve usually results in a momentary stall during an acceleration from the idle condition. Thus, there is a definite need in the art to improve engine operating performance and fuel efficiency through more precise control of throttle valve operation. There is also a need to increase the reliability of electronic throttle valves in case of electronics failure and especially to allow safe emergency operation.